U.S. patent application number 12/088415 was filed with the patent office on 2009-11-12 for gas-barrier material, method of producing the same and gas-barrier packing material.
This patent application is currently assigned to TOYO SEIKAN KAISHA, LTD.. Invention is credited to Aki Endo, Yusuke Obu, Hiroshi Sasaki.
Application Number | 20090280334 12/088415 |
Document ID | / |
Family ID | 37899480 |
Filed Date | 2009-11-12 |
United States Patent
Application |
20090280334 |
Kind Code |
A1 |
Obu; Yusuke ; et
al. |
November 12, 2009 |
GAS-BARRIER MATERIAL, METHOD OF PRODUCING THE SAME AND GAS-BARRIER
PACKING MATERIAL
Abstract
A gas-barrier material comprising a polycarboxylic acid polymer
(A) and a compound (B) having two ring structures (b) each of which
forming an ether bond to carbon that forms a double bond with
nitrogen and containing oxygen in the ether bond, wherein a
crosslinked structure is formed by the reaction of a carboxyl group
in the polycarboxylic acid polymer (A) with one of the ring
structures (b) of the compound (B). The gas-barrier material
features excellent gas-barrier property, retort resistance and
flexibility, can be cured at a low temperature within short periods
of time, and can be excellently produced.
Inventors: |
Obu; Yusuke; ( Kanagawa,
JP) ; Sasaki; Hiroshi; (Kanagawa, JP) ; Endo;
Aki; (Kanagawa, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
TOYO SEIKAN KAISHA, LTD.
Chiyoda-ku, Tokyo
JP
|
Family ID: |
37899480 |
Appl. No.: |
12/088415 |
Filed: |
June 2, 2006 |
PCT Filed: |
June 2, 2006 |
PCT NO: |
PCT/JP2006/311566 |
371 Date: |
March 27, 2008 |
Current U.S.
Class: |
428/424.2 ;
428/523; 525/329.9 |
Current CPC
Class: |
C08F 8/30 20130101; Y10T
428/31938 20150401; C08F 8/30 20130101; C08F 2810/20 20130101; C08F
8/30 20130101; Y10T 428/31573 20150401; C08F 120/06 20130101; C08F
120/06 20130101; B32B 27/08 20130101; C08F 8/44 20130101 |
Class at
Publication: |
428/424.2 ;
428/523; 525/329.9 |
International
Class: |
B32B 27/30 20060101
B32B027/30; B32B 27/40 20060101 B32B027/40; C08F 8/30 20060101
C08F008/30 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2005 |
JP |
2005-282008 |
Nov 8, 2005 |
JP |
2005-323298 |
Dec 13, 2005 |
JP |
2005-358790 |
Claims
1. A gas-barrier material comprising a polycarboxylic acid polymer
(A) and a compound (B) having two ring structures each of which
contains a double bond and an ether bond, the double bond being
formed between a carbon atom and a nitrogen atom, the ether bond
containing an oxygen atom and the carbon atom, wherein a
crosslinked structure is formed by the reaction of a carboxyl group
in said polycarboxylic acid polymer (A) with one of the ring
structures.
2. A gas-barrier material according to claim 1, wherein at least
one of the ring structures (b) contained in said compound (B) is an
oxazoline group or a derivative thereof.
3. A gas-barrier material according to claim 1, wherein said
compound (B) is a 2,2'-bis(2-oxazoline).
4. A gas-barrier material according to claim 1, wherein said
polycarboxylic acid polymer (A) is a poly(meth)acrylic acid or a
partly neutralized product thereof.
5. A gas-barrier material according to claim 1, wherein said
compound (B) is contained in an amount of 2 to 60 parts by weight
per 100 parts by weight of the polycarboxylic acid polymer (A).
6. A gas-barrier material according to claim 1, comprising the
polycarboxylic acid polymer (A) and forming two amido ester bonds
at the crosslinking portion.
7. A gas-barrier material according to claim 1, wherein metal ionic
crosslinking is formed by polyvalent metal ions among the remaining
unreacted carboxyl groups.
8. A method of producing a gas-barrier material by forming a metal
ionic crosslinking among the remaining unreacted carboxyl groups by
treating the gas-barrier material of claim 1 with water containing
a polyvalent metal compound.
9. A method of producing a gas-barrier material of claim 1 by
mixing together the polycarboxylic acid polymer (A) having a water
content of not larger than 15% and the compound (B).
10. A method of producing a gas-barrier material according to claim
9, wherein a metal ionic crosslinking is formed among the remaining
unreacted carboxyl groups by treating, with water containing a
polyvalent metal compound, the gas-barrier material formed by
mixing said polycarboxylic acid polymer (A) and the compound (B)
together.
11. A packing material having a layer of the gas-barrier material
of claim 1 on the surface of a plastic base material or between the
plastic layers.
12. A packing material according to claim 11, wherein the layer of
said gas-barrier material is formed on the surface of a plastic
base material via an anchoring layer, or at least one surface
thereof is formed between the plastic layers via the anchoring
layer.
13. A packing material according to claim 12, wherein said
anchoring layer contains an urethane polymer.
Description
TECHNICAL FIELD
[0001] The present invention relates to a gas-barrier material
obtained by using a crosslinking agent that comprises a compound
having a particular functional group for a polycarboxylic acid
polymer. More specifically, the invention relates to a gas-barrier
material having gas-barrier property, retort resistance and
flexibility, to a method of producing the same and to a packing
material obtained by using the gas-barrier material.
BACKGROUND ART
[0002] A variety of gas-barrier resins have heretofore been used as
represented, particularly, by polyvinylidene chloride,
polyacrylonitrile and ethylene/vinyl alcohol copolymer. From the
environmental reasons, however, use of the polyvinylidene chloride
and the polyacrylonitrile has not been recommended while the
ethylene/vinyl alcohol copolymer is accompanied by such problems
that the gas-barrier property is much dependent upon the humidity
and deteriorates under highly humid conditions.
[0003] To impart gas-barrier property to packing materials, there
has also been known to use a film obtained by depositing an
inorganic material on the surface of a base material. The deposited
film, however, is very expensive and still involves problems with
regard to flexibility and adhesion to the base material or to any
other resin layer.
[0004] In order to solve the above problems, there have been
proposed a gas-barrier film obtained by forming, on the base
material, a film which comprises aqueous high molecules A,
water-soluble or water-dispersing high molecules B and an inorganic
stratified compound (JP-A-9-151264), a gas-barrier film obtained by
applying a layer containing a metal compound onto the surface of a
formed layer of a mixture of a poly(meth)acrylic acid polymer and
polyalcohols (JP-A-2000-931) and a gas-barrier coating material
containing a polyvinyl alcohol, an ethylene/maleic acid copolymer
and a metal compound having a valency of two or more
(JP-A-2004-115776).
DISCLOSURE OF THE INVENTION
[0005] The gas-barrier materials disclosed in the above prior arts
may exhibit improved gas-barrier properties under highly humid
conditions but are not still capable of meeting a variety of
requirements as packing materials and are not satisfactory yet.
[0006] That is, in the gas-barrier film disclosed in the above
JP-A-9-151264, the inorganic stratified compound is simply
dispersed in the film. To obtain an excellent gas-barrier property,
therefore, the inorganic stratified compound must be added in large
amounts arousing a problem of a decrease in the mechanical strength
and retort resistance. According to JP-A-2000-931, the gas-barrier
film must be cured through the heat treatment conducted at a high
temperature and for an extended period of time. The gas-barrier
coating material disclosed in JP-A-2004-115776, too, must be
heat-treated at a high temperature when it is to be cured in short
periods of time. In particular, the gas-barrier materials disclosed
in JP-A-2000-931 and JP-A-2004-115776 are accompanied by problems
in regard to serious effect upon the plastic base material and
productivity.
[0007] It is therefore an object of the present invention to
provide a gas-barrier material which features excellent gas-barrier
property, retort resistance and flexibility, which can be cured at
a low temperature within short periods of time, and which can be
excellently produced without accompanied by the above problems.
[0008] Another object of the present invention is to provide a
method of producing the above gas-barrier material and a packing
material by using the above gas-barrier material.
[0009] According to the present invention, there is provided a
gas-barrier material comprising a polycarboxylic acid polymer (A)
and a compound (B) having two ring structures each of which
contains a double bond and an ether bond, the double bond being
formed between a carbon atom and a nitrogen atom, the ether bond
containing an oxygen atom and the carbon atom, wherein a
crosslinked structure is formed by the reaction of a carboxyl group
in said polycarboxylic acid polymer (A) with one of the ring
structures.
[0010] In the gas-barrier material of the present invention, it is
desired that:
1. At least one of the ring structures (b) contained in the
compound (B) is an oxazoline group or a derivative thereof; 2. The
compound (B) is a 2,2'-bis(2-oxazoline); 3. The polycarboxylic acid
polymer (A) is a poly(meth)acrylic acid or a partly neutralized
product thereof; and 4. The compound (B) is contained in an amount
of 2 to 60 parts by weight per 100 parts by weight of the
polycarboxylic acid polymer (A).
[0011] According to the present invention, there is further
provided a gas-barrier material comprising the polycarboxylic acid
polymer (A) and forming two amido ester bonds at the crosslinking
portion.
[0012] According to the present invention, there is further
provided a method of producing a gas-barrier material in which a
metal ionic crosslinking is formed by polyvalent metal ions among
the remaining unreacted carboxyl groups of the gas barrier
material.
[0013] According to the present invention, there is further
provided a method of producing a gas-barrier material in which a
metal ionic crosslinking is formed among the remaining unreacted
carboxyl groups by treating the gas-barrier material with water
containing a polyvalent metal compound.
[0014] According to the present invention, there is further
provided a method of producing a gas-barrier material by mixing
together the polycarboxylic acid-type polymer (A) having a water
content of not larger than 15% and the compound (B).
[0015] In this method of producing the gas-barrier material, too,
it is desired to treat the gas-barrier material that is formed with
water containing the polyvalent metal compound to thereby form a
metal ionic crosslinking among the remaining unreacted carboxyl
groups.
[0016] According to the present invention, there is further
provided a packing material having a layer of the gas-barrier
material or of the metal ionically crosslinked gas-barrier material
on the surface of the plastic base material or between the plastic
layers.
[0017] In the packing material of the present invention, it is
desired that:
1. the layer of the gas-barrier material or of the metal ionically
crosslinked gas-barrier material is formed on the surface of a
plastic base material via an anchoring layer, or at least one
surface thereof is formed between the plastic layers via the
anchoring layer; and 2. the anchoring layer contains an urethane
polymer.
[0018] The gas-barrier material of the present invention exhibits
excellent gas-barrier property and water resistance and, further,
exhibits excellent gas-barrier property even after subjected to
high temperature and wet heated conditions such as of retort
sterilization, making it possible to impart retort resistance.
[0019] Further, the gas-barrier material of the invention makes it
possible to easily form a crosslinked structure through the heating
at a low temperature within a short period of time and, hence, to
form an excellent gas-barrier material maintaining good
productivity without adversely affecting the plastic base
material.
[0020] Owing to its excellent flexibility, further, the gas-barrier
material of the invention can be used as a flexible packing
material without deteriorating the gas-barrier property caused by
damaging the gas-barrier material, and the gas-barrier material can
be formed on a plastic base material to obtain a multi-layer
pre-forming material, which can be further processed.
[0021] Upon introducing a metal ionic crosslinked structure among
the carboxyl groups remaining unreacted after the crosslinking by
using a crosslinking agent containing a polycarboxylic acid polymer
and a particular functional group, further, it is made possible to
strikingly improve the gas-barrier property under highly humid
conditions.
[0022] By mixing together the polycarboxylic acid polymer (A)
having a water content of not larger than 15% and the compound (B),
further, it is allowed to easily form a crosslinked structure at a
low temperature and in a short period of time making it possible to
further decrease adverse effect on the plastic base material, to
shorten the time required for the production and to further
decrease energy requirement.
[0023] By forming the gas-barrier material on the surface of the
plastic base material via an anchoring layer or by forming the
gas-barrier material between the plastic layers, the adhesion among
the layers can be markedly enhanced, and the mechanical strength
and flexibility of the packing material can be further
improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a view illustrating, in cross section, the
structure of a laminate prepared in Example 1;
[0025] FIG. 2 is a view illustrating, in cross section, the
structure of a laminate prepared in Example 9; and
[0026] FIG. 3 is a view illustrating, in cross section, the
structure of a laminate prepared in Example 11.
BEST MODE FOR CARRYING OUT THE INVENTION
[0027] A gas-barrier material of the present invention comprises a
polycarboxylic acid polymer (A) and a compound (B) having two ring
structures (b) each of which forming an ether bond to carbon that
forms a double bond with nitrogen and containing oxygen in the
ether bond, wherein an important feature resides in that a
crosslinked structure is formed by the reaction of a carboxyl group
in the polycarboxylic acid polymer (A) with one of the ring
structures (b) of the compound (B).
[0028] That is, in the gas-barrier material of the present
invention as represented by the following formula (1), the carboxyl
group in the polycarboxylic acid polymer (A) reacts with one of the
ring structures (b) in the compound (B) to form an amido ester to
thereby form a crosslinked film forming two amido ester bonds at
the crosslinking portion imparting excellent gas-barrier
property.
##STR00001##
[0029] The reasons why the gas-barrier material of the present
invention exhibits excellent gas-barrier property are presumably
due to that:
i) The polymer which is a chief component is a polycarboxylic acid
polymer and, hence, the carboxyl group on the side chain exhibits a
high hydrogen-bonding property producing a strong cohesive force,
making it possible to form a basic structure having excellent
gas-barrier property; ii) An amido ester bond which is a structure
effective in obtaining gas-barrier property is formed by the
reaction of the carboxyl group on the polymer side chain with the
ring structure (b) in the compound (B) which is a crosslinking
component; iii) The ring structures (b) are existing in a number of
two which is a minimum number required for forming the crosslinked
structure and, hence, the structure at the crosslinked point
spreads little three dimensionally, forming a densely crosslinked
structure that exhibits excellent gas-barrier property; and iv) Use
of the polycarboxylic acid polymer as the main component makes it
possible to metal ionically crosslink the unreacted carboxyl groups
that are not otherwise used for the crosslinking, to further
improve gas-barrier property under highly humid conditions and to
impart excellent gas-barrier property that does not deteriorate
even under highly humid conditions.
[0030] Further, the polycarboxylic acid polymer (A) is crosslinked
with the compound (B) at a low temperature and in a short period of
time little affecting the plastic base material on which a
gas-barrier material is to be formed, and offering a great
advantage from the standpoint of productivity.
[Polycarboxylic Acid Polymer (A)]
[0031] As the polycarboxylic acid polymer used for the gas-barrier
material of the present invention, there can be exemplified
polyacrylic acid, polymethacrylic acid, polymaleic acid,
polyitaconic acid, a homopolymer or a copolymer of a monomer having
a carboxyl group, such as acrylic acid/methacrylic acid copolymer,
as well as partly neutralized products thereof. Desirably, however,
there can be used polyacrylic acid or polymethacrylic acid.
[0032] The partly neutralized products of the polycarboxylic acid
polymer can be partly neutralized with a metal hydroxide such as
sodium hydroxide or potassium hydroxide, or ammonia.
[0033] Though there is no particular limitation, it is desired that
the degree of neutralization of the partly neutralized product is
not more than 30% as a mol ratio to the carboxyl groups. When the
degree of neutralization exceeds the above range, the
hydrogen-bonding property of the carboxyl group decreases and the
gas-barrier property deteriorates.
[0034] Though there is no particular limitation, it is desired that
the polycarboxylic acid polymer has a weight average molecular
weight in a range of 2,000 to 5,000,000, preferably, 5,000 to
1,500,000 and, particularly, 10,000 to 1,000,000.
[Compound (B)]
[0035] In the gas-barrier material of the present invention, the
compound (B) used as a crosslinking agent for crosslinking the
polycarboxylic acid polymer, has two ring structures (b) each of
which forming an ether bond to carbon that forms a double bond with
nitrogen and contains oxygen in the ether bond, i.e., each of which
ring structure having a group --N.dbd.C--O-- or an exoimino group
with a portion .dbd.C--O-- in the ring. Not being limited thereto
only, however, there can be exemplified the following ring
structures.
##STR00002##
[0036] In the case of the ring structure without oxygen in the
ether bond as represented by the following formula (2),
##STR00003##
on the other hand, there takes place no crosslinking reaction for
forming an amido ester bond to the polycarboxylic acid polymer. A
single ring structure cannot form the crosslinking. When there are
three or more ring structures, the structure at the crosslinking
point expands three dimensionally failing to form a densely
crosslinked structure having excellent gas-barrier property, which
is not desirable. Because of these reasons, what are important are
that a double bond is formed by nitrogen and carbon, carbon is
forming an ether bond, an ether bond is formed to carbon that is
forming a double bond with nitrogen and, in addition to these
conditions, that there are contained two ring structures (b) each
of which forming an ether bond to carbon that is forming a double
bond with nitrogen, and containing oxygen in the ether bond.
[0037] The compound (B) used for the gas-barrier material of the
present invention has two ring structures (b) that are described
above. The two ring structures may be the same or different. Here,
however, it is desired that at least one of them is an oxazoline
group or a derivative thereof.
[0038] As the compound (B) having two such ring structures (b),
through not limited thereto only, there can be exemplified
bisoxazolines such as 2,2'-bis(2-oxazoline),
2,2'-bis(4-methyl-2-oxazoline), 2,2'-bis(5-methyl-2-oxazoline),
2,2'-bis(5,5'-dimethyl-2-oxazoline),
2,2'-bis(4,4,4',4'-tetramethyl-2-oxazoline),
2,2'-p-phenylenebis(2-oxazoline), 2,2'-m-phenylenebis(2-oxazoline),
2,2'-o-phenylenebis(2-oxazoline),
2,2'-p-phenylenebis(4-methyl-2-oxazoline),
2,2'-p-phenylenebis(4,4-dimethyl-2-oxazoline),
2,2'-m-phenylenebis(4-methyl-2-oxazoline),
2,2'-m-phenylenebis(4,4'-dimethyl-2-oxazoline),
2,2'-ethylenebis(2-oxazoline), 2,2'-tetramethylenebis(2-oxazoline),
2,2'-hexamethylenebis(2-oxazoline),
2,2'-octamethylenebis(2-oxazoline),
2,2'-decamethylenebis(2-oxazoline),
2,2'-ethylenebis(4-methyl-2-oxazoline),
2,2'-tetramethylenebis(4,4-dimethyl-2-oxazoline),
2,2'-3,3'-diphenoxyethanebis(2-oxazoline),
2,2'-cyclohexylenebis(2-oxazoline) and
2,2'-diphenylenebis(2-oxazoline); and bisoxazines such as
2,2'-methylenebis(5,6-dihydro-4H-1,3-oxazine),
2,2'-ethylenebis(5,6-dihydro-4H-1,3-oxazine),
2,2'-propylenebis(5,6-dihydro-4H-1,3-oxazine),
2,2'-butylenebis(5,6-dihydro-4H-1,3-oxazine),
2,2'-hexamethylenebis(5,6-dihydro-4H-1,3-oxazine),
2,2'-p-phenylenebis(5,6-dihydro-4H-1,3-oxazine),
2,2'-m-phenylenebis(5,6-dihydro-4H-1,3-oxazine),
2,2'-naphthylenebis(5,6-dihydro-4H-1,3-oxazine), and
2,2'-p.p'-diphenylenebis(5,6-dihydro-4H-1,3-oxazine).
[0039] From the standpoint of mechanical properties and coloring,
in the present invention, it is desired that the crosslinking
portion formed by the polyacrylic acid polymer (A) and the compound
(B) comprises an aliphatic chain. Among the above compounds (B),
therefore, it is desired to use the one without aromatic ring and,
particularly, to use 2,2'-bis(2-oxazoline).
[Production of the Gas-Barrier Material]
[0040] The gas-barrier material of the present invention can be
produced by heating a coating composition containing the compound
(B) in an amount of 2 to 60 parts by weight and, particularly, 4 to
40 parts by weight per 100 parts by weight of the polycarboxylic
acid polymer (A) at a temperature of 110 to 170.degree. C. for 5
seconds to 5 minutes (peak-holding time) though these conditions
may vary depending upon the kinds of the polycarboxylic acid
polymer (A) and the compound (B) that are used or depending upon
the amount of applying the coating composition.
[0041] The above coating composition can be prepared by dissolving
the polycarboxylic acid polymer (A) and the compound (B) in water
or by mixing together the aqueous solutions of the above
components. In addition to water, there can be used a solvent such
as alcohol or a mixed solvent such as of water/alcohol and the
like.
[0042] There may be further added an acid catalyst to accelerate
the reaction of the carboxyl group of the polycarboxylic acid
polymer (A) with one of the ring structures (b) of the compound
(B). As the acid catalyst, there can be used a monovalent acid such
as acetic acid, propionic acid, ascorbic acid, benzoic acid,
hydrochloric acid, paratoluenesulfonic acid or alkylbenzenesulfonic
acid, and divalent or more highly valent acid such as sulfuric
acid, sulfurous acid, phosphoric acid, phosphorous acid,
hypophosphorous acid, polyphosphoric acid, pyrophosphoric acid,
maleic acid, itaconic acid, fumaric acid or polycarboxylic
acid.
[0043] To obtain the gas-barrier material of the invention, the
coating composition may be directly formed into a sheet or a film
which is, then, heated to form a crosslinked structure to thereby
obtain the gas-barrier material. Or, the coating composition
applied onto the base material is heated to form a crosslinked
structure and is, thereafter, removed from the base material to
obtain a gas-barrier material of a single layer. Or, the
gas-barrier layer is formed on a plastic base material to obtain a
multi-layered gas-barrier material.
[0044] In the gas-barrier material forming the crosslinked
structure, the unreacted carboxyl groups are remaining without
being used for forming the crosslinked structure. In the present
invention, therefore, it is particularly desired to form a metal
ionic crosslinking among the carboxyl groups that are remaining
unreacted to decrease the amount of the unreacted carboxyl groups,
to markedly improve water resistance, to further introduce the
ionically crosslinked structure into the crosslinked structure of
the polycarboxylic acid polymer, to impart more densely crosslinked
structure and to strikingly improve gas-barrier property under
particularly highly humid conditions.
[0045] It is desired that the metal ionic crosslinking is such that
the carboxyl groups are crosslinked with metal ions in an amount
corresponding to at least not smaller than an acid value of 100
mg/g KOH and, preferably, not smaller than 330 mg/g KOH in the
gas-barrier material.
[0046] To form the metal ionic crosslinking among the unreacted
carboxyl groups remaining in the gas-barrier material that is
forming the crosslinked structure, the gas-barrier material is
treated with water containing a polyvalent metal compound to easily
form a metal ionically crosslinked structure.
[0047] Treatment with water containing the polyvalent metal
compound can be executed by (i) a method of immersing the
gas-barrier material in water containing the polyvalent metal
compound, (ii) a method of spraying water containing the polyvalent
metal compound onto the gas-barrier material, (iii) a method of
placing the gas-barrier material under a highly humid condition
after the treatment (i) or (ii), or (iv) a retort treatment with
water containing the polyvalent metal compound (preferably, a
method which brings the packing material into direct contact with
hot water).
[0048] The above treatment (iii) is for imparting the effect of
aging after the treatments (i) or (ii), and enables the treatment
(i) or (ii) to be executed in a short period of time. In any of the
treatments (i) to (iii), the treating water that is used may be
cold water. In order for the water containing the polyvalent metal
compound to act on the gas-barrier material, however, the
temperature of the water containing the polyvalent metal compound
is maintained to be not lower than 20.degree. C. and, particularly,
from 40 to 100.degree. C. In the case of the treatment (i) or (ii),
the treating time is not shorter than 3 seconds and, particularly,
about 10 seconds to about 4 days. In the case of the treatment
(iii), the treatment (i) or (ii) is effected for not less than 0.5
seconds and, particularly, about one second to about one hour and,
thereafter, the treatment by atmosphere by placing the gas-barrier
material under a highly humid condition is conducted for not
shorter than one hour and, particularly, about 2 hours to about 14
days. In the case of the above treatment (iv), the treating
temperature is not lower than 101.degree. C. and, particularly, 120
to 140.degree. C., and the treatment is conducted for not shorter
than one second and, particularly, about 3 seconds to about 120
minutes.
[0049] Further, the gas-barrier material formed by using a coating
solution in which the polyvalent metal compound has been dissolved
or dispersed in advance, may similarly be treated with water or
water which contains the polyvalent metal compound.
[0050] There is no particular limitation on the polyvalent metal
ions so far as they are capable of crosslinking the carboxyl groups
possessed by the resin. Desirably, however, the polyvalent metal
ions have valencies of not smaller than 2 and, particularly, 2 to
3. Preferably, there can be used divalent metal ions such as
magnesium ions Mg.sup.2+ calcium ions Ca.sup.2+ and the like
ions.
[0051] As the metal ions, there can be exemplified alkaline earth
metals (magnesium Mg, calcium Ca, strontium Sr, barium Ba, etc.),
metals (iron Fe, ruthenium Ru, etc.) of the Group 8 of periodic
table, metals (copper Cu, etc.) of the Group 11 of periodic table,
metals (zinc Zn, etc.) of the Group 12 of periodic table, and
metals (aluminum Al, etc.) of the Group 13 of periodic table. As
the divalent metal ions, there can be exemplified magnesium ions
Mg.sup.2+ calcium ions Ca.sup.2+, strontium ions Sr.sup.2+, barium
ions Ba.sup.2+, copper ions Cu.sup.2+ and zinc ions Zn.sup.2+. As
the trivalent metal ions, there can be exemplified aluminum ions
Al.sup.3+ and iron ions Fe.sup.3+. The metal ions can be used in
one kind or in a combination of two or more kinds. As the
water-dissociating metal compound which is a source of the above
polyvalent metal ions, there can be exemplified metal salts
constituting the above metal ions, such as halides (e.g., chlorides
like magnesium chloride and calcium chloride), hydroxides (e.g.,
magnesium hydroxide, calcium hydroxide), oxides (e.g., magnesium
oxide, calcium oxide), carbonates (e.g., magnesium carbonate,
calcium carbonate), inorganic acid salts such as perhalogenates
(e.g., perchlorates like magnesium perchlorate and calcium
perchlorate), sulfates, sulfites (e.g., magnesium sulfonate,
calcium sulfonate), nitrates (e.g., magnesium nitrate, calcium
nitrate), hypophosphite, phosphite, phosphates (e.g., magnesium
phosphate, calcium phosphate), organic acid salts such as
carboxylates (e.g., acetates like magnesium acetate and calcium
acetate).
[0052] These metal compounds can be used in one kind or in a
combination of two or more kinds.
[0053] Among these compounds, further, it is desired to use halides
and hydroxides of the above metals.
[0054] It is desired that the polyvalent metal compound is present
in water in an amount of not smaller than 0.125 mmols/L, desirably,
not smaller than 0.5 mmols/L and, more desirably, not smaller than
2.5 mmols/L calculated as metal atoms.
[0055] In any treatment, further, it is desired that the water
containing the polyvalent metal compound is neutral to
alkaline.
[0056] The gas-barrier material of the present invention may
contain an inorganic dispersant in addition to the above
gas-barrier resin. The inorganic dispersant has a function of
blocking the water content from the outer side and protecting the
gas-barrier resin, and works to further improve the gas-barrier
property and water resistance.
[0057] The inorganic dispersant may have any shape such as
spherical shape, needle-like shape or stratified shape, but is the
one that exhibits wettability to the gas-barrier resin and
favorably disperses in the coating solution. From the standpoint of
blocking the water content, in particular, there is preferably used
a silicate compound having a stratified crystal structure, such as
water-swelling mica or clay. It is desired that the inorganic
dispersant has an aspect ratio of not smaller than 30 but not
larger than 5,000 from the standpoint of being dispersed in a
stratified manner to block the water content.
[0058] It is desired that the inorganic dispersant is contained in
an amount of 5 to 100 parts by weight per 100 parts by weight of
the gas-barrier resin.
[0059] The gas-barrier material of the present invention has a
gas-barrier ability sufficient for use as a retort packing
material, and exhibits excellent gas-barrier property permitting
oxygen to pass through in an amount of not larger than 10
cc/m.sup.2/day/atm (in an environment of 25.degree. C. and 80% RH)
even after subjected to the retort, as well as excellent retort
resistance.
[0060] To obtain the gas-barrier material of the invention at a low
temperature and in a short period of time, the coating composition
may be prepared by mixing the polycarboxylic acid polymer (A)
having a water content of not larger than 15% and the compound (B)
together. To suppress the water content to be not larger than 15%,
the polycarboxylic acid polymer may be put to the dehydration
treatment such as heating or reduction of pressure prior to
preparing the coating composition. It is desired that the water
content is not larger than 15% and, particularly, not larger than
10%.
[0061] By carrying out the production method of the invention, the
coating composition needs be heated at a low temperature for a
short period of time, i.e., at a temperature of 110 to 170.degree.
C. for 0 to 60 seconds (peak-holding temperature), further
suppressing adverse effect of heating on the plastic base material,
shortening the time required for the production and consuming
energy in decreased amounts.
[0062] The dehydration treatment can be effected to a sufficient
degree in an electric oven being heated at a temperature of 140 to
180.degree. C. for about 5 to about 20 minutes. Moreover, any other
heating means may be employed. There may be further executed a
processing such as a reduction of pressure or a combination of
heating with the reduction of pressure.
[0063] The water content in the polycarboxylic acid polymer is
found based on the Karl Fischer's method. The water content found
by the Karl Fischer's method varies depending upon the conditions
for heating the polycarboxylic acid polymer for vaporizing the
water content. If the heating condition is set to be lower than
200.degree. C., the amount of water (amount of free water) adsorbed
by the polycarboxylic acid polymer can be grasped. However, it
becomes difficult to find the water content inclusive of the water
content possessed as structural water by the polycarboxylic acid
polymer which has a high hydrogen-bonding property. When the
heating condition exceeds 250.degree. C., on the other hand, the
polycarboxylic acid polymer tends to be decomposed to a striking
degree, which is not desirable.
[0064] Therefore, to find the water content inclusive of both the
free water and the structural water, it is considered that a
preferred range of the heating condition is 200 to 250.degree. C.
As for the water content in the present invention, the heating
condition is set to be 230.degree. C. for vaporizing the water
content.
[0065] When the production method of the present invention is
employed, the solvent used in the step of preparing the coating
composition must be chiefly the one other than water, i.e., must be
the one having a heat capacity for volatilization smaller than that
water. Preferred examples of the solvent include methanol, ethanol
and isopropanol. Among them, methanol is particularly desired.
(Packing Material)
[0066] In the packing material of the present invention, the
gas-barrier material is formed on the surface of the plastic
substrate or between the plastic layers.
[0067] As the plastic base material, there can be exemplified any
packing material in the form of a film, a sheet, a bottle, a cup, a
tray or a can obtained from a thermoplastic resin that can be
heat-formed by extrusion forming, injection forming, blow forming,
draw-blow forming or press forming.
[0068] Suitable examples of the resin constituting the plastic base
material include olefinic polymers such as low-, intermediate- or
high-density polyethylene, linear low-density polyethylene,
polypropylene, ethylene/propylene copolymer, ethylene/butene
copolymer, ionomer, ethylene/vinyl acetate copolymer and
ethylene/vinyl alcohol copolymer; polyesters such as polyethylene
terephthalate, polybutylene terephthalate, polyethylene
terephthalate/isophthalate and polyethylene naphthalate; polyamides
such as nylon 6, nylon 6,6, nylon 6,10 and metaxylylene adipamide;
styrene polymers such as polystyrene, styrene/butadiene block
copolymer, styrene/acrylonitrile copolymer and
styrene/butadiene/acrylonitrile copolymer (ABS resin); vinyl
chloride copolymers such as polyvinyl chloride, and vinyl
chloride/vinyl acetate copolymer; acrylic copolymers such as
polymethyl methacrylate, methyl methacrylate/ethyl acrylate
copolymer; and polycarbonate.
[0069] These thermoplastic resins may be used in a single kind or
in the form of a blend of two or more kinds. Further, the plastic
base material may be of a single-layer constitution or a
laminated-layer constitution of two or more layers obtained by
co-melt extrusion or based on any other lamination.
[0070] To the above melt formable and thermoplastic resin, there
may, as required, be added one or two or more kinds of additives
such as pigment, antioxidant, antistatic agent, ultraviolet
absorber or lubricant in a total amount in a range of 0.001 part to
5.0 parts per 100 parts by weight of the resin, as a matter of
course.
[0071] In order to reinforce the container, furthermore, there may
be blended a fibrous reinforcing material such as glass fiber,
aromatic polyamide fiber, carbon fiber, pulp or cotton linter;
powdery reinforcing material such as carbon black or white carbon;
or flake-like reinforcing material such as glass flakes or aluminum
flakes, in one kind or in two or more kinds in a total amount of 2
to 150 parts by weight per 100 parts by weight of the thermoplastic
resin. As a filler, further, there may be added one or two or more
kinds of heavy to soft calcium carbonate, mica, talc, kaolin,
gypsum, clay, barium sulfate, alumina powder, silica powder and
magnesium carbonate in a total amount of 5 to 100 parts by weight
per 100 parts by weight of the thermoplastic resin according to a
known recipe.
[0072] In order to improve the gas-barrier property, further, there
may be added scale-like inorganic fine powder, such as
water-swelling mica or clay in a total amount of 5 to 100 parts by
weight per 100 parts by weight of the thermoplastic resin according
to a known recipe.
[0073] According to the present invention, the above-mentioned
gas-barrier material can be provided on the surface of the final
film, sheet or container, or the film thereof can be formed in
advance on a pre-formed article that is to be formed into a
container. As the pre-formed articles, there can be exemplified a
cylindrical parison with or without bottom which is to be biaxially
draw-blow formed, a pipe which is to be formed into a plastic can,
a sheet to be put to the vacuum forming, compressed air forming, or
plug-assisted forming, as well as a heat-sealed closure, and a film
for forming bags and pouches.
[0074] In the packing material of the present invention, it is
desired that the gas-barrier material, usually, has a thickness of
0.1 to 10 .mu.m and, particularly, 0.5 to 5 .mu.m. When the
thickness is smaller than the above range, the oxygen-barrier
property often becomes insufficient. Even when the thickness
exceeds the above range, on the other hand, there is not obtained
any particular advantage but rather disadvantage is brought about
from the standpoint of cost of the packing material. The
gas-barrier material can be provided as a single layer on the inner
surface of the container, on the outer surface of the container and
as an intermediate layer of a laminated body and can, further, be
provided as a multiplicity of layers on the inner and outer
surfaces of the container, or on either the inner surface or the
outer surface of the container and as the intermediate layer of the
laminated body, as a matter of course.
[0075] The film-coated pre-formed article can be formed into a
final container under the conditions known per se. such as biaxial
draw-blow forming or plug-assisted forming. Further, the film or
sheet coated with a layer may be stuck to another film or sheet to
form a laminated body which is, then, used as a pre-formed article
from which heat-sealed closures, pouches and containers are to be
formed.
[Anchoring Layer]
[0076] When used as the packing material, at least the one surface
of the layer comprising the gas-barrier material may be provided
with an anchoring layer. Provision of the anchoring layer enhances
the adhesion between the layers to further improve mechanical
strength of the container and the flexibility of the laminated
body. When the layer of the gas-barrier material is to be used as
the inner and outer surfaces of the container or as the outermost
layer of the laminated body, the layer of the gas-barrier material
may be formed via the anchoring layer. When the layer of the
gas-barrier material is to be formed as the intermediate layer of
the laminated body, the anchoring layer may be formed on at least
one surface of the layer of the gas-barrier material.
[0077] In the packing material of the present invention, the
anchoring member can be comprised of various polymers such as those
of urethane type, epoxy type, acrylic type and polyester type. It
is particularly desired that the packing material of the invention
contains an urethane polymer.
[0078] Further, the anchoring member may be comprised of a chief
agent and a curing agent, and may be a precursor in a state where
the curing reaction has not been completed or in a state where the
curing agent is present in an excess amount. In the case of the
urethane type, for example, the anchoring member is chiefly
constituted by a polyol component such as polyester polyol or
polyether polyol, and a polyisocyanate component. The
polyisocyanate component may be present in such an amount that the
number of the isocyanate groups in the polyisocyanate component is
greater than the number of the hydroxyl groups in the polyol
component.
[0079] It is desired that the polyol component used for forming the
urethane-type polymer is a polyester polyol. As the polyester
polyol, there can be exemplified the one obtained by the reaction
of a polyvalent carboxylic acid, a dialkyl ester thereof or a
mixture thereof with glycols or with a mixture thereof.
[0080] As the polyvalent carboxylic acid, there can be exemplified
aromatic polyvalent carboxylic acids such as isophthalic acid,
terephthalic acid and naphthalenedicarboxylic acid; and aliphatic
polyvalent carboxylic acids such as adipic acid, azelaic acid,
sebacic acid and cyclohexanedicarboxylic acid.
[0081] As the glycol, there can be exemplified ethylene glycol,
propylene glycol, diethylene glycol, butylene glycol, neopentyl
glycol and 1,6-hexane diol.
[0082] It is desired that the polyester polyol has a glass
transition temperature of -50.degree. C. to 100.degree. C. and,
preferably, -20.degree. C. to 80.degree. C. It is further desired
that the polyester polyol has a number average molecular weight of
1,000 to 100,000 and, preferably, 3,000 to 80,000.
[0083] As the polyisocyanate used for forming the urethane-type
polymer, there can be exemplified aromatic polyisocyanates such as
2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene
diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane
diisocyanate, 2,4'-diphenylmethane diisocyanate,
2,2'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenylene
diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate,
3,3'-dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene
diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, xylylene
diisocyanate and tetramethylxylylene diisocyanate; aliphatic
polyisocyanates such as tetramethylene diisocyanate,
1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate,
trimethylhexamethylene diisocyanate, 1,3-cyclohexylene
diisocyanate, 4-cyclohexylene diisocyanate, hydrogenated xylylene
diisocyanate, lysine diisocyanate, isophorone diisocyanate,
4,4'-dicyclohexylmethane diisocyanate, and
3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate; polyfunctional
polyisocyanate compounds such as isocyanurate derived from the
above polyisocyanate monomer, binret and allophanate; and
polyfunctional polyisocyanate compounds containing a terminal
isocyanate group obtained by the reaction with a trifunctional or
more highly functional polyol compound such as trimethylolpropane
or glycerin.
[0084] In the packing material of the present invention, though
there is no limitation, the anchoring layer is formed by heating a
coating composition which contains a polyisocyanate in an amount of
1 to 100 parts by weight and, particularly, 5 to 80 parts by weight
per 100 parts by weight of the above-mentioned polyester polyol at
a temperature of 60 to 170.degree. C. for 2 seconds to 5 minutes
depending upon the kinds of the polyester polyol and the
polyisocyanate and depending upon the amount of applying the
coating composition.
[0085] The above coating composition can be prepared by dissolving
the polyester polyol and the polyisocyanate in a solvent such as
toluene, MEK, cyclohexanone, Sorbesso, isophorone, xylene, ethyl
acetate or butyl acetate which is used in one kind or in a mixed
solution thereof, or can be prepared by mixing together the
solutions of the above components. In addition to the above
components, there can be used widely known cure promoting catalyst,
filler, softening agent, anti-aging agent, stabilizer, adhesion
promoter, leveling agent, defoaming agent, plasticizer, inorganic
filler, stickiness-imparting resin, fibers, coloring agent such as
pigment, and a usable time extender.
[0086] It is desired that the thickness of the anchoring layer is
0.01 to 10 .mu.m, preferably, 0.05 to 5 .mu.m and, more preferably,
0.1 to 3 .mu.m. When the thickness is smaller than the above range,
the effect of the anchoring layer does not often contribute to the
adhesiveness. When the thickness becomes greater than the above
range, on the other hand, no distinguished advantage is obtained
but rather disadvantage is brought about from the standpoint of
cost of the packing material.
[0087] In the packing material of the invention, if the anchoring
layer is provided to enhance the adhesion between the layers, the
laminated body exhibits further enhanced flexibility and does not
permit an increase in the oxygen permeation amount after the
laminated body is repetitively folded.
EXAMPLES
[0088] The invention will be further described by way of Working
Examples to which only, however, the invention is in no way
limited.
(Amount of Oxygen Permeation)
[0089] The amounts of oxygen that has permeated through the
laminated body of the obtained plastic films were measured by using
an oxygen permeation measuring instrument (OX-TRAN2/20,
manufactured by Modern Control Co.). The amounts of oxygen that has
permeated were also measured after having conducted the retort
sterilization treatment at 120.degree. C. for 30 minutes. The
measuring conditions were an environmental temperature of
25.degree. C. and a relative humidity of 80%.
Example 1
[0090] A polyacrylic acid (25% aqueous solution manufactured by
Wako Junyaku Co.) was used as the polycarboxylic acid polymer (A),
dry-solidified under a reduced pressure, and was immediately
dissolved in ethanol to obtain an (ethanol/water) solution (I)
containing 18.7% of solid component. The solvent composition
consisted of ethanol/water=80/1.3 as a weight ratio. Further, a
2,2'-bis(2-oxazoline) (manufactured by Tokyo Kasei Co.) was used as
the compound (B), and was dissolved in a mixed solvent of
ethanol/water (=16/3, weight ratio) to obtain an (ethanol/water)
solution (II) having a solid content of 5%. The solutions (I) and
(II) were so mixed together that the amount of the compound (B) was
5% by weight relative to the polycarboxylic acid polymer (A), and
were further so adjusted that the solid content was 10% and that
the weight ratio of the mixed solvent was ethanol/water=85/15
followed by stirring to prepare a coating solution.
[0091] By using a bar coater, the above coating solution was
applied onto a biaxially drawn polyethylene terephthalate film 2
having a thickness of 12 .mu.m. After the application, the above
film was heat-treated in a gas oven under the conditions of a peak
temperature of 140.degree. C. and a peak temperature-holding time
of 60 seconds to obtain a polyethylene terephthalate film having a
coating layer 3 of a thickness of 2 .mu.m. Into the tap water
maintained at 50.degree. C., calcium chloride was added in an
amount of 3.75 mmols calculated as metal atoms per a liter of tap
water, and the above film was immersed therein a whole day. After
taken out from the hot water and dried, the film was placed with
the coating layer as the lower layer. Onto the film were
successively laminated an urethane-type adhesive 4 in a thickness
of 2 .mu.m, a biaxially drawn nylon film 5 in a thickness of 15
.mu.m, an urethane-type adhesive 6 in a thickness of 2 .mu.m and an
undrawn polypropylene film 7 in a thickness of 70 .mu.m to obtain a
laminated body 1 of a layer structure as shown in FIG. 1.
Example 2
[0092] A laminated body was obtained by the same method as that of
Example 1 with the exception of mixing the solutions (I) and (II)
so that the amount of the compound (B) was 10% by weight relative
to the polycarboxylic acid polymer (A).
Example 3
[0093] A laminated body was obtained by the same method as that of
Example 1 with the exception of mixing the solutions (I) and (II)
so that the amount of the compound (B) was 20% by weight relative
to the polycarboxylic acid polymer (A).
Example 4
[0094] A laminated body was obtained by the same method as that of
Example 1 with the exception of mixing the solutions (I) and (II)
so that the amount of the compound (B) was 40% by weight relative
to the polycarboxylic acid polymer (A).
Example 5
[0095] A laminated body was obtained by the same method as that of
Example 1 with the exception of mixing the solutions (I) and (II)
so that the amount of the compound (B) was 60% by weight relative
to the polycarboxylic acid polymer (A) and that the solid content
was 8%.
Example 6
[0096] A polyacrylic acid (25% aqueous solution manufactured by
Wako Junyaku Co.) was used as the polycarboxylic acid polymer (A),
and 5 mol % thereof was neutralized by the addition of a 0.5 N
sodium hydroxide aqueous solution with good stirring. To the above
aqueous solution was added the solution (II) of Example 1 so that
the amount of the compound (B) was 10% by weight relative to the
polycarboxylic acid polymer (A), which was, then, diluted with
ethanol so that the solid content was 10% to thereby prepare a
coating solution.
[0097] By using the above coating solution, a laminated body was
obtained by the same method as that of Example 1.
Example 7
[0098] A polyethylene terephthalate film having a coating layer was
obtained by the same method as that of Example 1 with the exception
of so mixing the solutions (I) and (II) together that the amount of
the compound (B) was 10% by weight relative to the polycarboxylic
acid polymer (A). The above film was retort-treated with the tap
water at 120.degree. C. for 30 minutes, and was taken out, dried
and laminated by the same method as that of Example 1 to obtain a
laminated body.
Example 8
[0099] A polyethylene terephthalate film having a coating layer was
obtained by the same method as that of Example 1 with the exception
of so mixing the solutions (I) and (II) together that the amount of
the compound (B) was 20% by weight relative to the polycarboxylic
acid polymer (A). A solution obtained by adding calcium chloride in
an amount of 7.5 mmols calculated as metal atoms to a liter of the
tap water, was uniformly sprayed onto the surface of the above
coating layer for 5 seconds. Immediately thereafter, the film was
left to stand in a container maintained in an environmental
temperature of 50.degree. C. at a relative humidity of 100% for 10
days. After taken out and dried, the film was laminated by the same
method as that of Example 1 to obtain a laminated body.
Example 9
[0100] A polyethylene terephthalate film having a coating layer
having a coating layer 3 on a 12 .mu.m-thick biaxially drawn
polyethylene terephthalate film 2 was obtained by the same method
as that of Example 1 with the exception of so mixing the solutions
(I) and (II) together that the amount of the compound (B) was 20%
by weight relative to the polycarboxylic acid polymer (A). With the
coating layer as the upper layer, there were successively laminated
an urethane-type adhesive 4 in a thickness of 2 .mu.m, a biaxially
drawn nylon film 5 in a thickness of 15 .mu.m, an urethane-type
adhesive 6 in a thickness of 2 .mu.m and an undrawn polypropylene
film 7 in a thickness of 70 .mu.m to obtain a laminated body 8 of a
layer structure as shown in FIG. 2. Into the tap water maintained
at 50.degree. C., calcium chloride was added in an amount of 2.5
mmols per a liter of tap water, and the above laminated body was
immersed therein for 14 hours, and was taken out from the hot water
and dried.
Example 10
[0101] A laminated body was obtained by the same method as that of
Example 1 with the exception of so mixing the solutions (I) and
(II) together that the amount of the compound (B) was 20% by weight
relative to the polycarboxylic acid polymer (A) and that the
polyethylene terephthalate film having the coating layer was not
immersion-treated.
Comparative Example 1
[0102] A laminated body was obtained by the same method as that of
Example 1 with the exception of using a coating solution prepared
by using a polyacrylic acid (25% aqueous solution manufactured by
Wako Junyaku Co.) as the polycarboxylic acid polymer (A) and an
ethylene glycol as the compound (B), so mixing them together that
the amount of (B) was 10% by weight relative to (A) followed by
dilution with water, so that the solid content was 10%.
Comparative Example 2
[0103] A laminated body was obtained by the same method as that of
Example 1 with the exception of using a coating solution prepared
by using a carbodiimide compound (40% aqueous solution of
Carbodirite V-02 manufactured by Nisshinbo Co.) as the compound (B)
in an amount of 40% by weight relative to the polycarboxylic acid
polymer (A) followed by dilution with water, so that the solid
content was 10%.
Comparative Example 3
[0104] A laminated body was obtained by the same method as that of
Example 1 with the exception of using a coating solution prepared
by using an isocyanate compound (WD-730 manufactured by
Mitsui-Takeda Chemical Co.) as the compound (B) in an amount of 20%
by weight relative to the polycarboxylic acid polymer (A) followed
by dilution with water, so that the solid content was 10%.
Comparative Example 4
[0105] A laminated body was obtained by the same method as that of
Example 1 with the exception of using a solution (II) of a
propylene glycol diglycidyl ether (Denacol EX-911M manufactured by
Nagase Chemtex Co.) as the compound (B), mixing the solutions (I)
and (II) together so that the amount of the propyleneglycol
diglycidyl ether was 13% by weight with respect to the
polycarboxylic acid polymer (A), and adding a paratoluenesulfonic
acid in an amount of 3% by weight with respect to the
polycarboxylic acid polymer (A).
[0106] Table 1 shows the measured results of the amounts of oxygen
that has permeated through the laminated bodies obtained in
Examples 1 to 10 and in Comparative Examples 1 to 4 before and
after the retort treatment. Examples 1 to 10 all exhibited good
barrier properties before and after the retort treatment.
(Evaluation of Flexibility)
[0107] After subjected to the retort sterilization treatment at
120.degree. C. for 30 minutes, a laminated body of the obtained
plastic films was cut into a size of 130 mm.times.100 mm, formed
into a cylinder of a diameter of 30 mm and a length of 130 mm and
was mounted on a Gerboflex tester. A crash treatment was conducted
100 times by using the Gerboflex tester in an environment of a
temperature of 23.degree. C. and a relative humidity of 50% RH. The
crash treatment of one time consisted of a twisting motion
(twisting angle of 180.degree. and a length of motion of 60 mm) and
a horizontal motion (length of motion of 20 mm).
[0108] Thereafter, the amount of oxygen permeation was measured as
described above and was compared with the amount of oxygen
permeation before the crash treatment, i.e., compared with the
amount of oxygen permeation after the retort sterilization
treatment.
Example 11
[0109] A polyester polyol (Byron 200 manufactured by Toyoboseki
Co.) was dissolved in an ethyl acetate/MEK mixed solvent (weight
ratio of 60/40) in an amount of 20% by weight. Into the solution, a
polyisocyanate (Sumijule N3300 manufactured by Sumika Bayer
Urethane Co.) and a di-n-butyltin dilaurate (manufactured by Wako
Junyaku Co.) were added in amounts of 60% by weight and 0.8% by
weight with respect to the polyester polyol followed by the
dilution with the above mixed solvent, so that the solid content
was 14% by weight to thereby prepare a coating solution for forming
the anchoring layer.
[0110] By using a bar coater, the above coating solution was
applied onto a 12 .mu.m-thick biaxially drawn polyethylene
terephthalate film 2, was heat-treated in a gas oven under the
conditions of a peak temperature of 80.degree. C. and a peak
temperature-holding time of 10 seconds to obtain a polyethylene
terephthalate film having an anchoring layer 9 of a thickness of
0.5 .mu.m.
[0111] The coating solution of Example 2 was applied onto the above
film as a base material to obtain a laminated body 10 by the same
method as that of Example 1.
Comparative Example 5
[0112] A laminated body was obtained by the same method as that of
Example 11 but without forming anchoring layer.
[0113] Table 2 shows the measured results of the amounts of oxygen
permeation before and after the retort-treated laminated bodies
obtained in Example 11 and in Comparative Examples 5 were subjected
to the crash treatment 100 times by using the Gerboflex tester.
Example 11 exhibited good barrier property permitting a little
increase in the amount of oxygen permeation even after the crash
treatment.
(Measurement of Water Content)
[0114] The polycarboxylic acid polymer (A) was subjected to a
predetermined dehydration treatment and, when cooling was
necessary, was quickly transferred into a desiccator containing
silica gel in sufficient amounts and was left to cool. After cooled
down to near room temperature, the water content of the
polycarboxylic acid polymer (A) was measured by using a coulometric
titration water content-measuring apparatus (Model CA-06
manufactured by Mitsubishi Kagaku Co.) relying upon the Karl
Fischer's method. The heating temperature for evaporating the water
content was 230.degree. C.
(Evaluation of Resistance Against Hot Water)
[0115] A predetermined coating solution was applied onto a 12
.mu.m-thick biaxially drawn polyethylene terephthalate film, and
was heat-treated under a predetermined heat-treating conditions to
obtain a polyethylene terephthalate film having a coating layer of
a thickness of 2 .mu.m. The film was subjected to the retort
sterilization treatment at 120.degree. C. for 30 minutes and,
thereafter, the surfaces of the film were washed and dried. When
the thickness of the coating layer has decreased by more than 10%
as compared to before the retort sterilization, the resistance
against hot water was regarded to be X. When a decrease in the
thickness was smaller than 10%, the resistance against hot water
was regarded to be 0.
Example 12
[0116] A polyacrylic acid (AC-10LHP manufactured by Nihon Junyaku
Co.) was used as the polycarboxylic acid polymer (A), was
heat-treated in an electric oven at 170.degree. C. for 10 minutes,
and was quickly added to a methanol solvent and was dissolved
therein so that the solid content was 15% to thereby obtain a
solution (III). Further, a 2,2'-bis(2-oxazoline) (manufactured by
Tokyo Kasei Co.) was used as the compound (B) to obtain a methanol
solution (IV) thereof having a solid content of 5%. The solutions
(III) and (IV) were mixed together so that the amount of the
compound (B) was 10% by weight with respect to the polycarboxylic
acid polymer (A), and were further adjusted with methanol with good
stirring so that the solid content was 8% to thereby obtain a
coating solution.
[0117] The above coating solution was applied by using a bar coater
onto a 12 .mu.m-thick biaxially drawn polyethylene terephthalate
film 2, and was heat-treated in an electric oven under the
conditions of a peak temperature of 140.degree. C. and a peak
temperature-holding time of 0 second to obtain a polyethylene
terephthalate film having a coating layer 3 of a thickness of 2
.mu.m.
Comparative Example 6
[0118] A polyacrylic acid (25% aqueous solution manufactured by
Wako Junyaku Co.) was used as the polycarboxylic acid polymer (A),
was dried and solidified under a reduced pressure, and was quickly
dissolved in methanol to obtain a methanol solution (V) having a
solid content of 18%. Further, the above solution (IV) was used as
the compound (B), and the solutions (V) and (IV) were mixed
together so that the amount of the compound (B) was 10% by weight
relative to the polycarboxylic acid polymer (A) followed by
adjustment with methanol with good stirring so that the solid
content was 13% to thereby obtain a coating solution.
[0119] A polyethylene terephthalate film having a coating layer of
a thickness of 2 .mu.m was obtained by the same method as that of
Example 12 but using the above coating solution.
[0120] Table 3 shows the water contents, resistance against hot
water and barrier properties of the polyethylene terephthalate
films having the coating layers obtained in Example 12 and in
Comparative Example 6. Example 0.12 exhibits good resistance
against hot water and good barrier properties.
TABLE-US-00001 TABLE 1 Compound (B) Polycarboxylic acid polymer (A)
Amount Neutralization (% by wt) Ex. 1 polyacrylic acid no
2,2'-bis(2-oxazoline) 5 Ex. 2 polyacrylic acid no
2,2'-bis(2-oxazoline) 10 Ex. 3 polyacrylic acid no
2,2'-bis(2-oxazoline) 20 Ex. 4 polyacrylic acid no
2,2'-bis(2-oxazoline) 40 Ex. 5 polyacrylic acid no
2,2'-bis(2-oxazoline) 60 Ex. 6 polyacrylic acid yes
2,2'-bis(2-oxazoline) 10 Ex. 7 polyacrylic acid no
2,2'-bis(2-oxazoline) 10 Ex. 8 polyacrylic acid no
2,2'-bis(2-oxazoline) 20 Ex. 9 polyacrylic acid no
2,2'-bis(2-oxazoline) 20 Ex. 10 polyacrylic acid no
2,2'-bis(2-oxazoline) 20 Comp. Ex. 1 polyacrylic acid no ethylene
glycol 10 Comp. Ex. 2 polyacrylic acid no carbodiimide compound 40
Comp. Ex. 3 polyacrylic acid no isocyanate compound 20 Comp. Ex. 4
polyacrylic acid no propyleme glycol diglycidyl ether 13 Uncoated
-- -- -- -- laminate O.sub.2 permeation amount Barrier layer
(cc/m.sup.2/day/atm) Formation of ionic position in Before After
crosslinking the laminate retort retort Remarks Ex. 1 immersed
lower layer 0.2 0.3 Ex. 2 immersed lower layer 0.2 0.2 Ex. 3
immersed lower layer 0.5 0.6 Ex. 4 immersed lower layer 1.5 1.2 Ex.
5 immersed lower layer 3.9 3.1 Ex. 6 immersed lower layer 0.4 0.3
Ex. 7 retort lower layer 0.2 0.3 Ex. 8 spray/atmosphere lower layer
1.5 0.9 Ex. 9 immersed surface layer 0.8 0.9 Ex. 10 -- lower layer
7.2 3.5 Comp. Ex. 1 -- lower layer 65 -- film dissolved during
retort Comp. Ex. 2 immersed lower layer 70 130 Comp. Ex. 3 immersed
lower layer 70 130 Comp. Ex. 4 immersed lower layer 12 100 Uncoated
-- -- 70 130 laminate
TABLE-US-00002 TABLE 2 O.sub.2 permeation Barrier amount layer
(cc/m.sup.2/day/atm) Polycarboxylic acid Compound (B) Formation
position After polymer (A) Amount of ionic in the Anchor Before
crashed Neutralization (% by wt) crosslinking laminate layer
crashing 100 times Ex. 11 polyacrylic no 2,2'-bis(2- 10 immersed
lower yes 0.2 5.3 acid oxazoline) layer Comp. polyacrylic no
2,2'-bis(2- 10 immersed lower no 0.2 9.8 Ex. 5 acid oxazoline)
layer
TABLE-US-00003 TABLE 3 Polycarboxylic acid Compound (B) Water
Resistance O.sub.2 permeation polymer (A) Amount content against
amount Neutralization (% by wt) (%) hot water (cc/m.sup.2/day/atm)
Ex. 12 polyacrylic no 2,2'-bis(2- 10 11 .smallcircle. 0.5 acid
oxazoline) Comp. Ex. 6 polyacrylic no 2,2'-bis(2- 10 18 x note)
acid oxazoline) note) Not measured for film has dissolved.
* * * * *